Solve 12x − 15 = 105

The solution of 12x − 15 = 105 is x = 10.

12x - 15 = 105\ \Rightarrow\ x = 10

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The lines y = 12x − 15 and y = 105 meet at x = 10. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$12x - 15 = 105$
2
Add 15 to both sides:
$12x - 15 + 15 = 105 + 15 \ \Rightarrow\ 12x = 120$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{120}{12} \ \Rightarrow\ x = 10$
4
Check: put x = 10 back into the equation.
$12\cdot10 - 15 = 120 - 15 = 105 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 15 = 105\ \Rightarrow\ x = 10 \]
\[ 12x - 15 = 105 \]
\[ 12x - 15 + 15 = 105 + 15 \ \Rightarrow\ 12x = 120 \]
\[ \frac{12x}{12} = \frac{120}{12} \ \Rightarrow\ x = 10 \]
\[ 12\cdot10 - 15 = 120 - 15 = 105 \checkmark \]

Trying values of x in 12x − 15 = 105

x	12x − 15	Equals 105?
8	81	no
9	93	no
10	105	yes
11	117	no
12	129	no

Questions

What is x in 12x − 15 = 105?

The solution of 12x − 15 = 105 is x = 10.

How do you solve 12x − 15 = 105?

Add 15 to both sides to get 12x = 120, then divide both sides by 12 to get x = 10.

How do I check the answer?

Replace x by 10: 12(10) − 15 = 105, which is 105.

Solve 12x − 15 = 105

How to work it out

Trying values of x in 12x − 15 = 105

Questions

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